One of the specs you'll hear thrown around when you're shopping for a CPU is the process node
measured in nanometers and how a smaller one is better. Just check out the tech headlines and
you'll see plenty of stories about how chip makers are racing to cram more and more tiny
transistors onto their processors. And why not? More transistors means better performance and
efficiency because the electrons don't have to travel as far through each transistor so they
can switch on and off and therefore process information more quickly. But do process nodes
really tell the whole story? To get some answers, we reached out to Jason Gorse and Bruce Feinberg
from Intel and we'd like to thank them for their contributions. The process node was originally a
measure of how long the gate in the transistor was. This is the part that actually controls the
flow of electrons from the source to the drain. This was considered an accurate enough proxy
for transistor size up until about 1997 when the 350 nanometer process was popular. The reason
this is important is because when you double the number of transistors on a chip, it's fair to
expect roughly double the performance at a given die size. And for a long time, these
doublings, if you will, took place at such predictable intervals that Moore's law came to be,
stating that the number of transistors on a chip would double about every two years.
This gave the chip makers an easy cadence to follow for naming each process node because they could
expect each one to be smaller by a factor of about 0.7. Why 0.7, you might ask? Well, the
transistors are roughly square in shape and if you multiply 0.7 by 0.7, you get 0.49 or roughly
one half. So for example, when the industry went from the 1000 nanometer process node to the 700
nanometer process node, this marked a rough doubling of the number of transistors that they
could fit in a given area, even though the name of the process only reduced by a factor of 0.7.
Thing is, in 1997, while manufacturers were able to start shrinking the gate length by more than a
factor of 0.7, other parts of the transistor weren't shrinking as quickly anymore. So gate
length was no longer a good proxy for the overall transistor density in the entire chip,
and therefore the performance. Rather than changing the naming scheme outright though,
we started to see a process node defined by the size of a group of transistors called a cell.
This was done to give people an estimate of the equivalent level of processing power
accounting for components that weren't shrinking as quickly. So the first node we saw under this
new naming system was the 250 nanometer process. Performance was about double the previous node,
as you would expect from the name, but the gate length was actually around 190 nanometers,
which is much smaller. It's just that there was other stuff that prevented the transistors from
being packed more tightly than that. This scheme involving cell area lasted until around 2012
and the 22 nanometer process when a whole new type of transistor was introduced, FinFET.
Chipmakers found that at these sizes, the gates were so small that you could have electrons leaking
through them due to quantum tunneling. This could cause undesirable behavior, so engineers needed
a way to make their chips more powerful without shrinking the gates even further. The solution
was to take the channel the electrons go through and raise it up like a shark fin, hence the name
increasing the surface area of the channel and allowing lots more electrons to pass through.
Of course, this also meant that transistors were now three-dimensional instead of planar,
making it much harder to accurately measure their size. Now the industry has still continued to use
that 0.7 factor to describe a generation of improvement, like going from 14 to 10 to 7
nanometer processes. But the truth of the matter is that these numbers don't actually measure the
real size of the transistor anymore, and they can even vary wildly between different manufacturers.
Intel, for example, attempts to measure a process node by taking the weighted average
of the two most common standard cell sizes. Really, a more important consideration though
is transistor density. That's how many can be packed into the same space without decreasing
the size of the actual transistor features very much, if at all. In addition to density,
chip makers are using other techniques like improved materials to boost performance.
This can include everything from squeezing the crystal structure of the channel to make the
electrons go through faster, to low resistance traces between transistors, to gate materials
with a high dielectric constant for better control of electron flow. Of course, this process can
require some trial and error. Intel's well-publicized difficulties with their 10 nanometer process
were due in large part to them trying to overscale. In other words, pack more than double the number
of transistors into the same space, which required them to try lots of new technologies inside the
chip all at one time, which caused delays and manufacturing problems. But as our technology
continues to improve, chip makers look poised to keep Moore's law, even if it's a little slower,
alive to some extent, as well as keep silicon, the base material for our processors, for a long
time to come before we have to really start considering more exotic solutions, like carbon
nanotubes. In the meantime, I hope you enjoyed this deeper dive into processor sizes. Just remember
that the process node isn't the be-all and end-all when you're shopping for a CPU anyway. It's
always more important to pay attention to the real-world performance that you'll see in games
and applications that you actually use. Thanks for watching, guys. Like, dislike, check out our
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